In the past, there is known, in Japanese Patent Application Laid-Open No. 8-169436 (Patent Document 1), a folding box made of cardboard which becomes a rectangular or square shape in a plan view in a state where the folding box is assembled into a box form by foldably connecting adjacent side ends of four front/rear/left/right side surfaces and is configured to be able to be folded flatly by being folded into an approximate parallelogram form in such a way that each corner of one pair of diagonal corners become an acute angle and each corner of the other pair of diagonal corners become an obtuse angle. The folding box of the above-mentioned form can be folded compact because the folding box is folded so that inner surfaces of the respective side surfaces on the front, rear, left and right overlap each other in a folded state and can be stored in a small space in an unused state. In folding the folding box, the folding box can be easily folded by being folded into an approximate parallelogram form in such a way that each corner of one pair of diagonal corners become an acute angle and each corner of the other pair of diagonal corners become an obtuse angle as described above. In forming the folding box into a box form, the folding box can be formed into a box form simply by being folded in such a way that the opposed corners become a right angle, in a reverse procedure to above. That is, this folding box has a characteristic that folding and assembly are easy.
However, the folding box made of cardboard is low in strength and easy to be broken. Further, the folding box made of cardboard tends to be soiled and, once soiled, the soil is hardly removed and cannot be cleaned. Because of these reasons, in a normal form of use, the folding box made of cardboard is disposed when the folding box is used only once. This is not preferable from a viewpoint of resource saving. Even if the folding box made of cardboard is reused, the folding box made of cardboard can be reused only three to five times since the folding box is low in strength, tends to be soiled, and, once soiled, the soil is hardly removed and cannot be cleaned as described above. A worker usually carries the folding box made of cardboard in such a manner as to grip a pair of opposed sides of a lower surface with both hands to hold the entire folding box. However, since an outer surface of the folding box made of cardboard is made slippery, there is a problem that the folding box is slippery and hard to be carried. When the worker carries the folding box made of cardboard in a manner other than the manner described above, for example, when the worker carries the folding box in such a manner that the worker grips one side portion of the lower surface with one hand and grips one side portion of an upper surface on a diagonal line of the box with the other hand, since a posture of the box made of cardboard is unstable, the box is more slippery and hard to be carried. In some cases, the worker carries the folding box made of cardboard in such various postures as to grip the folding box upside down or with the front and rear or the left and right reversed with both the hands or gripping corners of a hexahedron with both the hands. In all the cases, the folding box made of cardboard is still slippery and hard to be carried. Moreover, when the folding box made of cardboard is tied with a string, there is a problem that the string is slippery and a position of the string moves or the folding box cannot be firmly tied. In this case, to make the string less slippery, the folding box made of cardboard only has to be tied stronger than necessary to cause the string to cut into the folding box made of cardboard. However, in this case, there is a problem that the folding box made of cardboard is damaged. Moreover, when not in use, a plurality of folding boxes made of cardboard are stored or transported in a state where each folding box is folded flatly and laid and stacked vertically. However, since the folding box made of cardboard is folded in a state where the center portion thereof is higher than outer ends thereof, a folded shape thereof is unstable. Therefore, when the folding boxes made of cardboard is placed in a state where the folding box tilts to one side end side with respect to the center in the vertically stacked state, the placement is unstable. Moreover, since the folding box is made of cardboard, the folding box is slippery. Because of these reasons, there is a problem that, when the folding boxes made of cardboard are stacked in a large number of stages in a state where the folding boxes are folded flatly, the folding boxes tend to collapse. Furthermore, when the folding boxes made of cardboard are vertically stacked in multiple stages and stored or transported in a state where the folding boxes are assembled into a box form and have contents therein, the folding box at an upper stage tends to slip with respect to the folding box at a lower stage and the folding boxes may collapse.
A folding box made of synthetic resin is proposed by Japanese Patent Application Laid-Open No. 8-282648 (Patent Document 2) as a folding box which can be folded and assembled into a box form in the same manner as the folding box made of cardboard and is compatible with the folding box made of cardboard. The folding box made of synthetic resin described in Patent Document 2 including hinge parts is entirely formed of hard synthetic resin, and the hinge parts are formed as thin parts of the hard synthetic resin.
The folding box made of synthetic resin described in Patent Document 2 has a characteristic that, while the folding box can be used in the same manner as the folding box made of cardboard in the past, the folding box made of synthetic resin is high in strength, dirt of the folding box is easily removed, and the folding box can be cleaned and reused many times compared with the folding box made of cardboard. However, the worker usually carries this folding box made of synthetic resin by gripping an opposed pair of edges at bottom ends with both the hands to hold the entire folding box in the same manner as the folding box made of cardboard. Since the portions to be gripped by the hands are made of the hard synthetic resin, there is a problem that the folding box is more slippery and harder to be carried than the folding box made of cardboard. When the folding box made of synthetic resin is carried in a manner other than the manner described above, since a posture of the folding box is unstable, the folding box is more slippery. Further, the worker carries this folding box made of synthetic resin in such various postures as to, in the same manner as the folding box made of cardboard, grip the folding box upside down or with the front and rear or the left and right reversed with both the hands or gripping corners of a hexahedron with both the hands. In all the cases, the folding box made of synthetic resin is slippery and hard to be carried, as described above. Moreover, when the folding box made of synthetic resin is tied with a string, because the folding box is made of synthetic resin, there is a problem that the string is more slippery and the position thereof shifts or the folding box cannot be firmly tied. Moreover, since the folding box made of synthetic resin is folded to be flat in the same manner as the folding box made of cardboard, a folded shape is unstable. Therefore, in transporting or storing the folding box made of synthetic resin, when a plurality of folding boxes made of synthetic resin are vertically stacked and stored or transported in a state where the folding boxes are folded flatly and laid to be flat in the same manner as the folding box made of cardboard, the folding boxes cannot be stably stacked. In particular, since the folding boxes in upper and lower stages are vertically stacked while side panels formed of hard synthetic resin are in contact with each other, the folding boxes are more slippery than the case of the cardboard. When the folding boxes of a synthetic resin are stacked in a large number of stages, there is a problem that the folding boxes more easily collapse. The folding boxes made of synthetic resin are also vertically stacked in multiple stages and stored or transported in a state where the folding boxes are assembled into a box form and have contents inside them. Since the folding box made of synthetic resin is more slippery than the folding box made of cardboard as described above, the folding box at an upper stage tends to slip with respect to the folding box in a lower stage and the folding boxes may collapse.
Furthermore, the folding box made of synthetic resin in the past described in Patent Document 2 is one component entirely molded by integral molding of synthetic resins. Thus, in the case of a large folding box, a size of a die increases, which causes an increase in cost.
There is also known, in Japanese Patent No. 3547763 (Patent Document 3), an assembled box made of synthetic resin formed by continuously connecting panels to be side surfaces to four sides of one panel to be a bottom through hinge elements, respectively, and continuously connecting a panel to be a lid surface to the panel to be the side surface through a hinge element.
This assembled box of Patent Document 3 is formed by integrally molding a plurality of hinge elements as a net with a first injection molding die using a first plastic material, molding the respective surfaces of the box by injecting a second plastic material into a second injection molding die in a state where this net is arranged in the second injection molding die, and insert-molding both sides of respective pieces of the net in the inside of ends of the panels to be the respective surfaces of the box made of the second plastic material. In this assembled box, projection tips of convex projecting parts provided in the net slightly project in a dot shape to outer surfaces of the ends of the panels to be the respective surfaces of the box made of the second plastic material, whereby additional friction is generated to prevent boxes from sliding with respect to each other.
However, in this assembled box described Patent Document 3, although nonslip parts are provided on the outer surfaces of the panels forming the surfaces of the hexahedral box, only the tips of the convex projecting parts projecting and exposed in the dot shape from the net buried in thickness of the ends of the panels function as the nonslip parts. Thus, an exposed area of the nonslip parts is extremely small and there is a problem that a nonslip effect cannot be sufficiently exercised. In particular, when a worker grips the hexahedral box with hands and carries the box, positions to be held varies from worker to worker and, moreover, positions where the hands and fingers touch vary depending on sizes and lengths of the hands and the fingers of the worker, a bending state of the hands and the fingers in gripping the box, and the like. Therefore, it cannot be said that the hands and the fingers surely grip the nonslip parts of the dot shape. Even if the hands and the fingers successfully touch the nonslip parts of the dot shape, since the nonslip parts are only formed in the dot shape, a sufficient nonslip effect can not be obtained in gripping the box with the hands because only slight friction acts on the parts of the hands and the fingers.
Here, in Patent Document 3, it is also conceivable to increase the area of the convex projecting parts and to increase the area of the exposed parts of the tips of the convex projecting parts exposed to the outer surfaces of the panels to come into contact with the hands and the fingers in a large area and improve the nonslip effect with friction. However, in the assembled box of Patent Document 3, both the sides of the respective pieces of the net are insert-molded in the inside of the ends of the panels to be the respective surfaces of the box made of the second plastic material. Thus, there is a problem that, when the area of the convex projecting parts is increased, the convex projecting parts hinder a flow of the second plastic material when the second plastic material is injected, the second plastic material hardly flows around to an opposite side of injection points of the convex projecting parts, the second plastic material cannot be sufficiently filled in this part, and the parts cannot be accurately insert-molded. Consequently, it is impossible to increase the area of the convex projecting part to increase the area of the nonslip parts of the tips of the projections. Therefore, the sufficient nonslip effect in gripping the box with the hands as described above is not obtained.
Furthermore, in the assembled box of Patent Document 3, the plurality of panels connected through the net are expanded to continue in a plane shape in a state where the box is disassembled when the box is not in use, and the box can not be folded to be small. Therefore, there is a problem that a plane area in storing or transporting the box in the state where the box is disassembled in the plane shape is large and a large space is necessary. Moreover, there is also a problem that it takes time to assemble and disassemble the box. Furthermore, as described above, since the box is disassembled in a plane shape when the box is not in use, there is a problem that the respective inner surfaces of the panels are exposed to the outside and the inner surfaces of the panels are soiled. Therefore, there is a problem that, in reusing the box, since the inner surfaces of the box are dirty, contents in the box may be soiled.
Furthermore, in Patent Document 3, the assembled box is obtained by insert-molding the net, which is obtained by integrally molding the plurality of hinge elements, when the surfaces of the box are molded in a separate injection molding die. Thus, there is a problem in that two types of injection molding dies, i.e., a first injection molding die for molding the net and a second injection molding die for insert-molding the net are necessary as injection molding dies, it is difficult to position and hold the net in a predetermined position in the second injection molding die, the molding takes time, and molding cost increases.